At present, a Wireless Fidelity system includes a Station (STA, i.e., a WiFi user), an Access Point (AP), an Access Controller (AC), a Broadband Remote Application Server (BRAS), a portal server, a Remote Authentication Dial-in User Service (RADIUS) and other nodes, and FIG. 1 illustrates a schematic diagram of the WiFi system networking.
In FIG. 1, an interface between the STA and the AP is an air interface for wireless transmission in compliance with the specifications of the protocols IEEE802.11a/b/g/n, etc. An interface between the AP and the AC/BRAS complies with the specification of the Control And Provisioning of Wireless Access Point Protocol (CAPWAP) for wired transmission.
An operation process of the WiFi network can be roughly divided into three phases:
In phase 1, the WiFi access point accesses the WiFi system, which is a procedure in which the AP is powered on and accesses the AC, where the AP can obtain an Internet Protocol (IP) address of the AP through the Dynamic Host Configuration Protocol (DHCP) and obtain an IP address of the AC through the DHCP Options43 attribute or Domain Name System (DNS) resolving or otherwise. The AP which has obtained the IP address of the AC initiates actively an authentication connection with the AC. The AC verifies the AP and then establishes a Control And Provisioning of Wireless Access Point Protocol (CAPWAP) tunnel connection with the AP. The AP can download a corresponding configuration file from the AC over the CAPWAP tunnel to obtain configuration information and configure itself.
In phase 2, the WiFi user is authenticated. Firstly the WiFi user obtains an IP address through the standard DHCP, Where the address is allocated by the AC/BRAS; and thereafter the WiFi user accesses a web server and initiates a Hyper Text Transfer Protocol (HTTP) request. The AC/BRAS intercepts the HTTP request and forces the user to be authenticated with the portal server. The portal server pushes a web authentication page to the WiFi user. The user fills a user name, a password and other information into the authentication page and submits them to the portal server. The portal server sends a user information query request to the Remote Authentication Dial-in User Service (RADIUS) upon reception of the user information, and the RADIUS server verifies the user information.
In phase 3, WiFi user data is transmitted. After the WiFi user is authenticated, the AP transmits WiFi user data to the AC/BRAS over the CAPWAP tunnel. Taking uplink data as an example, an IP header in a CAPWAP message is filled as illustrated in FIG. 2, where the CAPWAP message includes an IP header, a User Datagram Protocol (UDP) header, a CAPWAP header and a CAPWAP payload, wherein the CAPWAP payload further includes an IP header and WiFi user data; and the IP header of the CAPWAP message is filled with slashes, and in the IP header of the CAPWAP message, a Source IP is the IP of the AP device, and a Target IP is the IP of the AC device; and the IP header of the CAPWAP payload is filled with vertical lines, and in the IP header of the CAPWAP payload, a Source IP is the IP of the WiFi user, and a Target IP is the IP of the accessed web.
As illustrated in FIG. 3, the operation process of the WiFi network includes the following steps:
The phase 1 includes the following steps:
In the step S301, the AP is powered on and initiates a DHCP request;
In the step S302, the AP obtains an IP address of the AP;
In the step S303, the AP Obtains an IP address of the AC;
In the step S304, the AP establishes a CAPWAP tunnel connection with the AC;
In the step S305, the AP configures itself;
In the step S306, the AC/BRAS allocates an IP address for the WiFi user; and
In the step S307, the WiFi user is authenticated and the data is transmitted.
The AP is an important transmitting medium in WiFi networking, and is typically connected with the AC/BRAS through a switcher, a router or other device in a wired connection manner. The wired connection manner may result in complicated and troublesome network wiring. The coverage area of the AP itself is small, so a large total number of APs may be required. Deployment of a sufficiently large number of APs outdoors means a high engineering cost and a long construction period.
Consequently, WiFi networking is typically limited to a hotspot indoors, and mobility may be supported poorly due to the technical characteristic of the WiFi system, on at least an interruption and even unavailability of a service may arise in some high mobility-demanding scenarios.